Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$70.26	11.347%	$78.2324	$78.23	$78.25	$78.20
Purchase #2	$91.97	8.792%	$100.056	$100.06	$100.05	$100.10
Purchase #3	$244.44	12.796%	$275.7185	$275.72	$275.70	$275.70
Purchase #4	$85.97	8.472%	$93.2534	$93.25	$93.25	$93.30
Purchase #5	$99.95	3.282%	$103.2304	$103.23	$103.25	$103.20
Purchase #6	$188.63	4.123%	$196.4072	$196.41	$196.40	$196.40
Purchase #7	$31.82	13.389%	$36.0804	$36.08	$36.10	$36.10
7 purchase totals =	$813.04		$882.9783	$882.98	$883.00	$883.00